An affordable injection-molded precision hybrid glass-polymer achromatic lens

This paper describes the development of an affordable precision hybrid glass-polymer achromatic doublet fabricated by microinjection molding. This hybrid lens can be used to correct chromatic aberration by combining a flint and a crown glass. Specifically, polycarbonate was selected as the flint glass with higher dispersion and N-BK7 was selected for lower dispersion crown glass. Microinjection molding was utilized to apply the aspherical polycarbonate layer directly onto the N-BK7 glass lens' surface in this study for its capabilities of precision microfeature replication and mass production. In addition, finite element-based numerical simulation for molding process was employed to assist the design to improve the manufacturability. To ensure high precision in the fabricated hybrid lens, mechanical alignment features were created on the mold inserts to position the finished polymer lens along with the insert that housed the glass lens. The mold inserts' surfaces were diamond-turned to optically finished without polishing. It was demonstrated in this study that with properly designed manufacturing processes, an integrated hybrid glass-polymer lens could be fabricated without further mechanical alignment. Lastly, the optical performance of the hybrid lens was verified by focal shift evaluation.